1. Field of the Invention
The present invention relates to a film cartridge and a camera. More particularly, this invention is concerned with a film cartridge having a display code that represents information of a built-in film using a pattern of electrodes set in array, and a camera using the film cartridge.
2. Description of the Related Art
As far as a roll film to be encased in a film cartridge is concerned, a means for identifying the type of the film has been proposed in Japanese Patent Laid-Open No. 57-202524 in the past. Herein, a code representing the sensitivity of the film is displayed on the outer surface of the film cartridge. By detecting the code, a film sensitivity suitable for the film is set automatically.
FIG. 1 shows an example of a DX code 53a displayed on an existing JIS 135-size film cartridge 53 for storing a perforated normal film 52a. The leader of the normal film 52a is pulled out. The DX code 53a has electrodes set in array. The electrodes L1 to L12 fall into conductors and insulators. The conductors are formed by baring the metal base of the circumferential surface of the film cartridge 53. The insulators are formed by coating the metal base with an insulating material. In FIG. 1, areas shown in black represent insulators. The detailed dimensions of the normal film are shown in FIGS. 25a and 25b, and listed in Table 1.
TABLE 1 ______________________________________ Symbol Dimension (mm) ______________________________________ A1 35 B1 4.75 C1 2.8 D1 1.98 E1 2.0 F1 25.4 R1 0.5 ______________________________________ Tolerances are omitted.
In the foregoing DX code 53a, the electrodes L1 and L7 are provided as earth electrodes. Continuity to the electrode L1 or L7 is detecting in each of the other electrodes (L2 to L6 and L8 to L12), thus acquiring film information the electrodes provide.
Table 2 presented below lists codes formed with electrodes L2 to L6 and identifying film sensitivities. Table 3 lists codes formed with electrode areas L8 to L10 and identifying numbers of film frames. Table 4 lists codes formed with electrode areas L11 and L12 and identifying permissible film latitudes.
TABLE 2 ______________________________________ ISO film Electrode area sensitivity 2 3 4 5 6 ______________________________________ 25 -- -- -- 0 -- 32 -- -- -- -- 0 40 -- -- -- 0 0 50 0 -- -- 0 -- 64 0 -- -- -- 0 80 0 -- -- 0 0 100 -- 0 -- -- 0 125 -- 0 -- -- 0 160 -- 0 -- 0 0 200 0 0 -- 0 -- 250 0 0 -- -- 0 320 0 0 -- 0 0 400 -- -- 0 0 -- 500 -- -- 0 -- 0 640 -- -- 0 0 0 800 0 -- 0 0 -- 1000 0 -- 0 -- 0 1250 0 -- 0 0 0 1600 -- 0 0 0 -- 2000 -- 0 0 -- 0 2500 -- 0 0 0 0 3200 0 0 0 0 -- 4000 0 0 0 -- 0 5000 0 0 0 0 0 ______________________________________
TABLE 3 ______________________________________ Number of Electrode area permissible exposures 8 9 10 ______________________________________ 12 0 -- -- 20 -- 0 -- 24 0 0 -- 36 -- -- 0 ______________________________________
TABLE 4 ______________________________________ Electrode area Latitude 11 12 ______________________________________ +1/2 -- -- +1 0 -- +2, -1 -- 0 +3, -1 0 0 ______________________________________
In Tables 2 to 4, a circle (o) indicates that the electrode is conducting electricity to the electrode L1 or L7. -- indicates that the electrode is not conducting electricity to the electrode L1 or L7. In an example of a film cartridge 53 of FIG. 1, the information specified with the electrodes L2 to L6 and L8 to L12 reveals that the film in the film cartridge 53 has a sensitivity of ISO 100, permits 24 exposures, and provides a latitude of +2/-1.
Japanese Patent Laid-Open No. 2-21570 has disclosed a camera in which two contacts are brought into contact with areas on a film cartridge 53 that correspond to earth electrodes of a DX code 53a simultaneously, and thus whether or not the film cartridge 53 has the DX code 53a is determined.
In Japanese Patent Laid-Open No. 56-36629, when a film cartridge 53 is mounted, the structure of a spool of the film cartridge is checked for any differences (depths of engagement holes formed on the spool). Then, the type of film stored in the film cartridge, and, for example, an ASA sensitivity of the film are identified, then exposure control is performed on the camera automatically.
In Japanese Patent Laid-Open No. 44-2540, an irregular section for setting a film sensitivity is formed on the outer surface of a film cartridge. The sensitivity of a film in the film cartridge is identified by detecting the irregular section, similar to the proposal of the Japanese Patent Laid-Open No. 56-36629. Then, exposure control is performed on the camera automatically.
On the other hand, a well-known camera that employs a roll film and switches photographic screen sizes has been disclosed in Japanese Patent Laid-Open No. 36-14234. The camera switches masking plates for photographic screens and sizes of a finder window simultaneously. Using the same camera, photographic screen sizes can be changed any time externally according to the purposes of photography and photographs can be taken. The spacing of photographic screens is made constant, and a shape of each photographic screen is displayed on the finder window.
Japanese Patent Laid-Open No. 58-142324 has disclosed a large-size camera designed for a Brownie film and capable of using a 135-size film. Herein, a film advancing drive to be operated using an advancing lever formed on a camera body is installed in the camera body so that a film take-up for the Brownie film and a film take-up for a 135-size film cartridge can be switched freely. In addition, a film advancing mechanism interlocked with the film advancing drive is incorporated in each of the Brownie film take-up and 135-size film cartridge take-up.
Japanese Patent Laid-Open No. 59-188623 has disclosed a film counter for a camera in which the information of the number of film frames recorded on the outer circumferential surface of a film cartridge is read to display the number of remaining film frames and the number of exposed film frames. Herein, the information of the number of film frames recorded on a film cartridge mounted in a camera is read electrically, and the read information is converted into the number of film frames and stored. A certain value is subtracted from the number of film frames every time a shutter is actuated, then the result of the subtraction is displayed.
A film encased in a 135-size film cartridge has perforations on its sides as stipulated in JIS Standard K7519-1982 "135-size Film Cartridge" or ISO Standard 1007 "Photography 135-size Film and Magazine Specification." Due to the presence of the perforations, only 25.4 mm is ensured as an effective photographic width for a film width of 35 mm. Therefore, as stipulated in JIS Standard B7115, the standard photographic screen size becomes 24 mm by 36 mm. The effective use rate in the direction orthogonal to the film feeding direction is given as 0.69 or a quotient of 24 by 35, which is smaller than 70%. Therefore, unlike photographs taken at a high effective use rate at which the width of a photographic screen is increased fully within a film width of 35 mm, photographs taken in the standard photographic screen size require higher enlargement ratios for printing. Thereby, the quality of print images deteriorates.
The perforations are designed for intermittent feeding of cinefilm, which are, therefore, not always required for normal still cameras. Then, when the perforations are abandoned to increase a photographic screen size, an enlargement ratio for printing can be reduced to provide high-quality print images.
However, when perforations are abandoned to produce an imperforated film, some measure must be taken to differentiate a perforated film from an imperforated film. Then, employment of an existing DX code 53a (See FIG. 1) has been devised.
However, in the existing DX code 53a, all electrodes have their assignments and cannot represent any other identification information. The DX code 53a is designed to represent the number of permissible film exposures on the assumption that a standard screen size of 24 mm by 36 mm is adopted (See FIG. 3). The film counter described in the Japanese Patent Laid-Open No. 59-188623 counts exposed film frames on a basis of the standard screen size. When photographic screens are enlarged, or especially, made wider than standard screens, and exposed, even if the film counter is used to display the number of exposed frames, it fails to display the number of remaining unexposed frames correctly.
In the existing DX code 53a, both electrodes L1 and L7 are established as earth electrodes. However, a function as an earth electrode is required only at one point. Therefore, either the electrode L1 or L7 need work as an earth electrode.
On the other hand, in any of conventional cameras capable of switching photographic screen sizes, photographic screens are switched manually and the switching mechanism is complex. As for a photographic screen switching means described in the Japanese Patent Laid-Open No. 36-14232, when a 135-size film cartridge is employed, photographic screens can merely be changed from a standard size of 24 mm .times.36 mm to a half size of 24 mm by 18 mm; that is, the size of each photographic screen can merely be changed in the film feeding direction. The length in the direction orthogonal to the film feeding direction cannot be changed. This means that small photographic screens or photographic screens of the half size can be provided and exposed easily. However, it is hard to provide photographic screens larger than the standard size, because enlargement can be done only in the feeding direction.
The art disclosed in the Japanese Patent Laid-Open No. 58-142324 is restricted to large-size cameras using a Brownie film or other large-sized film but cannot apply to cameras supporting only a 135-size film cartridge. Changing photographic screen sizes means loading different films of different sizes. When only, for example, a 135-size film cartridge is in use, photographic screens cannot be changed.